Since Sigil 7.x is based on Qt 5, I assumed that it supports HTML5/CSS3 to the extent that it's supported by Webkit.
However, it seems that the unicode-range descriptor is being ignored by Sigil 7/Qt 5.

which should apply the embedded blackletter font only to uppercase letters in the div section. However, in Book View, all letters were displayed in the blackletter font. Is this another Qt issue or is this behavior by design?
(Since my old Kindle 3 applied the embedded font correctly, I assume that the styles are OK.)